Current production of hydrogen (H2) emits carbon dioxide (CO2), but an alternative is to use heat to directly decompose methane (CH4) at high temperatures (700-1400° C.), which can be cleaner and cheaper. H2 is primarily used to manufacture ammonia for fertilizer (e.g., food production), as well as in refinery processes for polymers and methanol. Global H2 production is responsible for approximately ˜5% of global CO2 emissions. The problem is that the direct decomposition of methane approach has been stifled by the formation of solid carbon products that eventually plug the reactor.
The current process for producing H2 from CH4 and water (H2O) fundamentally relies on a thermodynamic driving force to form CO2 and to liberate H2. Since current methods emit CO2 and are not penalized for this externality, the cost of producing H2 is very low, and has been extremely difficult for alternative processes to compete with. There are other ways, however, of producing H2, such as the direct thermal cracking of CH4, which does not produce CO2 and instead yields solid carbon C(s) (e.g., carbon black (CB)) as a side product, which is much more lucrative than CO2. In the direct thermal cracking of CH4, the decomposition reaction occurs completely above 1400° C. and is driven by the increased entropy associated with obtaining two gaseous molecules (2·H2) instead of one (CH4), and also the strong bonds associated with solid carbon phase. The problem with this approach is that conversion of a gas to another gas with a solid byproduct is inherently problematic, because one must contain the gasses within some type of solid vessel and the solid byproduct will deposit on the solid vessel walls. This leads to eventual failure of the reactors as the solid byproduct build-up eventually clogs and blocks the flow path for the gasses, effectively plugging the reactor. Thus, the primary issue with direct thermal cracking of methane has been the plugging problem. The inability to make a reactor that operates continuously with a long lifetime is the key issue, because the economics of thermal CH4 cracking are highly favorable.